Hydraulic pressure transmitter



May 31, 1949. e. w. HARDY HYDRAULIC PRESSURE TRANSMITTER 2 Sheets-Sheet 1 Filed March 22, 1945 v 1 INVENTOR GORDON W HARDY ATTORNEY Ma 31, 1949. G. w. HARDY 2,471,619

HYDRAULIC PRESSURE TRANSMITTER Filed March 22, 1943 2 Sheets-Sheet 2 GORDON M4 HARDY ATTORNEY Patented May 31, 1949 UNITED STATES PATENT OFFICE Claims.

This invention relates to fluid pressure producing devices or hydraulic actuators, and more particularly to hydraulic actuators suitable for use in hydraulic motor transmitting systems such as are employed, for example, as part of the steering mechanism for marine craft, airplanes, and

other vehicles.

Many types of primary fluid pressure producing devices or hydraulic actuators adapted to be used to impa'rt'motion to secondary hydraulically operable devices include a cylinder, a piston reciprocable in the cylinder, and a rotatable member passing through at least one wall of the cylinder for imparting motion to the piston as through a screw threaded connection with the piston. Since in such actuator devices high fluid pressure is produced alternately on opposite sides of the piston, difiiculty has been experienced in adequately sealing the rotatable member against fluid leakage without introducing high friction forces tending to prevent free turning of the rotatable member, and tending to produce rapid deterioration of the sealing means. Also, difficulty has been experienced in such hydraulic actuators due to leakage of fluid from the system resulting in lost motion or hydraulic back lash notwithstanding the provision of reservoir supply means tending to compensate for such leakage.

In accordance with this invention an improved hydraulic actuator system is provided having"- ment which does nottend to bind the screw shaft against free turning and which is not subjected "to the usualinfiuences tending to wear the sealing material used therein.

The general object of this invention is .to provide an improved fluid pressure producing device or hydraulic actuator.

Another object is to provide a hydraulic actu-" ator and fluid source combination having improved means for preventing flow of fluid from the actuator to the source while permitting free how of the fluid from the source to the actuator at 'all times.

A more specific object is to provide, in a hydraulic actuator including a cylinder having a port in its wall arranged to "communicate with a fluid source, a simplified and readily adjustable means permitting unidirectional flow of fluid between the source and the cylinder.

A still more specific object is to provide a simplified valve assembly of the spring biased ball type between a fluid supply source and the cylinder of a hydraulic actuator.

A further object is .to provide a hydraulic actuator including a screw or worm driven piston which has improved means for sealing the rotatable screw or worm shaft against fluid leakage.

A still further object is to provide means for eliminating the necessity for packing between a rotatable screw shaft and the cylinder wall of a hydraulic actuator through which the shaft passes.

Another specific object is to provide, on a piston which is reciprocated by a rotatable screw shaft, an elongated sleeve extension which surrounds and is reciprocable axially with respect to the rotatable screw shaft and thereby eliminate th necessity for providing packing in contact with the shaft to prevent fluid leakage around the shaft at the point where it enters the cylinder in which the piston reciprocates.

Still another object is to provide an elongated sleeve extension on a screw driven piston which cooperates with the cylinder in which the piston moves to seal the rotatable screw shaft against fluid leakage and to prevent rotation of the piston.

Other objects and advantages of this invention will become apparent from the following description of a preferred form shown in the drawings, wherein:

Fig. 1 is a simplified schematic View of a fluid pressure motion transmitting system in which the fluid pressure producing device of this invention may be used;

Fig, 2 is a cut-away perspective view of the fluid pressure producing device;

Fig. 3 is a sectional view taken generally at 33 in Fig. 2; and

Fig. 4 is an enlarged schematic view (not in scale with Fig. 2) illustrating the means for controlling unidirectional fluid flow from a supply source tothe actuator.

Referring to Figs. 1 and 2, the fluid pressure producing device ll] of this invention comprises generally a piston assembly I I .arranged to move within a cylinder [2 as a result of rotation of a screw shaft 14 havinga coarse (e. g. square type) threaded portion 15 passing through a complementary threaded opening in a hub portion l6 :of a traveling nut member'l -'l of the piston assembly H. The screw shaft M may be driven man- .the cylinder 33. I 35 and 35' extending through opposite ends of ually through suitable gearing such as shown in my Patent 2,178,073, issued October 31, 1939, or by a prime mover such as a reversible electric motor M and control means therefor, not shown. The piston assembly H, which will be described in detail hereinafter, comprises generally, in addition to the traveling nut member ll, annular elastic face members l8 and I3 which seal against the cylinder and tubular sleeve extensions 20 and 2|.

The cylinder i2 is provided with outlet ports 23 and 24 in its wall near opposite ends and on opposite sides of the piston assembly II which communicate, through respective passages 25 and 2-6 in a base portion 21, with a pair of exterior outlet ports 28 and 29, respectively. Suitable openings 3|] are provided in the base portion 21 for convenience in mounting the device It].

Conduits 3| and 32 are threaded into the ports 28 and 23, respectively, and extend to a suitable fluid pressure translating device such as the secondary cylinder 33, the conduits being arranged,

for example, to supply fluid respectively to opposite sides of a double-ended piston 34 slidable in The piston 34 has piston rods the secondary cylinder 33 which are provided at their outer ends with suitable couplings 36 and 36' respectively, by means of which the piston rods 35 and 35 may be readily attached to any desired mechanism, such as a boat steering mechanism, for accomplishing steering operations in accordance with the movements of the piston 34.

A fluid source 31 is arranged to maintain a supply of suitable hydraulic fluid, such as oil, to the cylinder |2 through a conduit 38 and passages, to be described later, in the top wall of the cylinder l2, the arrangement being such that the cylinder l2 and 33 and the interconnectin conduits 3| and 32 are automatically maintained full of fluid at all times.

As thus shown and described, rotation of the screw shaft I4 as by the motor M in a direction causing the piston assembly II to move to the right forces fluid from the right hand end of the cylinder I2 through the outlet port 24, the passage 26, and the conduit 32 to the right hand end of the secondary cylinder 33. This results in an increased fluid pressure in the right hand end of the cylinder 33, and, since movement of the piston assembly H to the right also reduces the fluid pressure in the left hand end of the cylinder 33 due to the interconnecting conduit 3|, the piston 34 moves to the left under the joint additive influence of a positive pressure force and. a negative or suction force to actuate the mechanism attached to the piston rods 35 and 35'. Obviously, rotation of the screw shaft M in the opposite direction so as to move the piston assembly l to the left causes the piston 34 to move to the right in a similar manner.

Referring more particularly to Fig. 2, the cylinder I2 is closed at its opposite ends by cylinder heads 39 and 43 having externally threaded tu-v bular extensions 4| and 42, respectively, the openings through the extensions continuin through the heads and being enlarged at their inner ends to provide additional space for reciprocation of the piston assembly I I.

The head 39 may be attached to the cylinder l2 as by suitable cap screws 45 which pass through circumferentially spaced openings in an outer flange portion 39' of the head 39 into complementary threaded sockets in the cylinder l2;- and an enlarged inner end 43 of a hollow axial into complementary threaded sockets in the cylbearing extension 41 is threaded over the extension 4|. The hollow axial bearing extension 41 has an outer reduced tubular portion 48 and a generally concave area 49 on its inner wall surface at the intersection of the portions 46 and 48 which defines, with an end surface 43 of the extension 4|, an annular generally V-shaped groove for receiving suitable packing 50. Similarly an annular skirted packing nut 5| is threaded on the extension 42 of the head 40 and has a generally concave area 52 which defines, with a corresponding area 44 0f the extension 42, an annular generally V-shaped groove for receiving suitable packing 53.

'An enlarged flanged tubular portion 54 of a bearing support 55 fits loosely over the packing nut 5| and has its flange 55' abutting the head 40. Suitable cap screws 55 pass through aligned spaced circumferential openings in the flange 55 and an outer flange portion 40 of the head 40 inder |2 to secure the head 40 and the hollow axial bearing extension 55 thereto. The bearing support 55 has a reduced central tubular portion 58 which merges into an outer portion 59 of generally ovate shape as shown, the openings through the tubular portion 58 continuing as by a pair of cap screws 5|, and has a central circular opening counterbored from its inner face to receive an anti-friction radial and axial thrust bearing assembly 62 (conical roller assembly as shown) for rotatably supporting the screw shaft M at a reduced outer end portion 34. The end portion '34 extends beyond the plate 6|] and has a keyway 65 and a threaded portion 36 at its outer end for attachment of a suitable coupling associated with the motor M or other driving means for the shaft I4. I

.An enlarged inner portion 68 of the shaft |4 defines with the portion 64 a shoulder which may operatively abut against the bearing assembly 32 and has the screw threaded portion |5 near its inner end which engages with the traveling screw threadednut member I! of the piston assembly I The inner end face of the shaft |4 operatively abuts against the inner end face of a thrust shaft 59 which is threaded into the hollow axial bearing extension 41 and which isprovided with a slot 10 in its outer end face so that it may be readily adjusted to determine the axial clearance of the shaft l4. To reduce friction, the inner end of the thrust shaft and adjacent end of the screw shaft may have a steel thrust ball 69' interposed therebetween in cupped ends of the two shafts complementary to the ball. A lock nut 1| holds the thrust shaft B9 in adjusted position. An inner non-threaded portion 12 of the piston sealing face members I8 and I9 are attached as by bolts 16.-and nuts 18 (bearingon metal shells 16' and 18) to opposite sides of a hub portions Hi to were reduced-outerperipheral portion 19 of the flange J5. The face members-have"thickened portions '80 and "8|,respe'ctively, at their outer peripherits so that fairly wide sealing surfaces are p're- I in accordance with this invention, the tubular .piston extensions 20 and 2ljof'the piston assembly i I have their inner ends in sealed relation to the traveling nut member '[1 as at'threaded connections of the extensions with counterbor'ed open'ingsat .opposite 'ends of the 'travelin'g'nut memberl'l. "Said sleeve extensions 20 and 2| areslidably received in the openingsthroughthe tubular extensions 4! and 42, respectively,of the heads '39 and 4B, and function as sleeve type bushings to rotatably support the screw shaft '14 in cooperation with the bearing assembly'62.

Thesleeve ex'tension'fll, which fits slidabl'y into the annular space 14 defined'by the packing'supipor't' '4"! and the reduced inner 'end portion 12 of the thrust shaft '69, has its outer surface operatively in engagement with the packing '50 to prevent fluid leakage from the left hand'end of the-cylinder 12.

As shown most clearly in Fig. 3, the sleeve extension 2! has 'equallyspaced and outwardly extending radial projections 8| at its outer end ""which are slidable in "complementary longitudinal grooves 82 in the splined portion of the inner wall surface of the hollow axial bearin extension 58 and flanged end portion 59 of I the associated housing member. spline type connection between the sleeve exten- 'siOn ill and the bearing support 59, rotation of the piston assembly H. is prevented. If desired set screws or looking pins (not shown) may be provided in anpbvious manner to lock the piston the sleeve extensions Zfl'and 2| at the threaded connections of the hub portions IE therewith. The outer surface of the sleeve extension 2| is oper'atively in engagement with the packing 53 and thereby fluid leakage from the right hand end of the cylinder I2 is prevented.

Assuming that the hydraulic fluid in the system is oil the main driving screw threads, bearing 62 and various sliding surfaces contact area between the sleeve extensions 211 and 2| and the adjacent parts described above can be lubricated by the almost negligible quantity of slip fluid which escapes from the main Working cylinder past one or the other of the seals and 53. Suitable pressure and suction relief channels or vents are, of course, provided, a in accordance with well known practice, for the generally closed spaces at the ends of the piston sleeve extensions 2|] and 2! to prevent dead pocketing and oil locking on part of the piston extensions. Two vent holes are indicated at 483: and 58x respectively on Fig. 2.

From the foregoing it is apparent that as the screw shaft l4 reversibly rotates upon reversible operation of the motor M, or other reversible driving means, to thereby reciprocate the piston assembly ll the sleeve extensions 20 and 2| slide freely back and forth in continuous engagement with the packing 50 and 53. The packings 50 and 53 consequently need only prevent fluid leakage between relatively sliding surfaces, and no packing is required between the rotating shaft I4 and the cylinder l2. The advantage of this arrangement is particularly important since it By virtue of this ing 85.

permits the thread po rt'ion'is or "the that u to pass through'the' cylinderliead' lfl, thus makingit possible to use "a shorter cylinder 1 2 than ent r- Wise would "be required and also "greatly simplifiesthe construction of the packing assemblies. v Referring now to Fig. 4 which shows most "clearly the'featur'e 'of 'this invention which insures a continuous'repl'enishm'ent'of fluid to the syste '0': which the actuator 10 or this'invention form's apart without any pjo'ssibility'of the occurrence"offhydraulic backlash, a thickened wall portion 84 at the topbfthe cylinder 12 has an axial opening 85 'ther'ethrough which "is cbuntertorearrom its opposite ends to define a pair of ball seats "85 and 85 'on opposite sides 'of an intermediate "intersecting opening 81 into which the conduit 35 (Fig. 1) is threaded. A

pair of openings 88 and 88 extend transversely through "the portion 84 and intersect the open- Valve'asse'mblie's 89 and 89' comprise a pair of screws '90 and "90 which are threaded into 'o'pposite "ends of the opening 85 and hold in 'adjusted position a pair of valve springs 91 and '91, rrespectively, the "thrust of which normally biases a pair of ball type valve plugs 92 and 92', "respectively, against the seats 86 and 86'. The plugs of the valve assemblies '89 and 89' are held in closed position by the springs SI and 91', respectivelyahd the pressurepr fluid in the cylinfd'er {2 to prevent flow of fluid from the cylinder [2 to the source, but move to open position against the biasof'the springs 9! and 91, respectively, by the hydraulic head of the source -31 and 'by suction'created by movement of the piston Fl whenever additional fluid is required to completely fill the hydraulic system with fluid. A continuous'su'pply of fluid for the system is thereby rendered available at all times, but hydraulic backlas' and reduced effici'enc'y is ef- 'fectivelyprevented. The outer ends of the open lugs 85, '88, and ill! may be sealed by ordinary screw plugs 93. The plugs 93 which 'are aligned with "the screws 90 and 90', when removed, enable s'a'id screws to be adjusted whereby to adjust and subs'ta'ntially equalize the seating force of the ball type valve plugs on their seats.

I claim:

1. In a hydraulic actuator, a cylinder, end caps secured on the ends of said cylinder, hollow axial bearing extensions screw threaded on said caps to provide a pair of aligned cylindrical internal bearing surfaces, a threaded shaft passing through said cylinder and into each of said aligned bearings and radially spaced therefrom, a piston with an axial opening in said cylinder, a tubular piston extension at each end of said piston, surrounding said shaft and extending into and journaled in respective hollow axial bearing extensions, an internal thread in said axial opening in said piston to engage thread on said shaft, and packing interposed between said caps and said hollow axial bearing extensions surrounding said tubular piston extensions at the ends of said pistons.

2. In a hydraulic actuator, a cylinder, end caps secured on the ends of said. cylinder, hollow axial bearing extensions screw threaded on said caps to provide a pair of aligned cylindrical internal bearing surfaces, a threaded shaft passing through said cylinder and into each of said aligned bearings and radially spaced therefrom, a piston with an axial opening in said cylinder, a tubular piston extension at each end of said piston, surrounding said shaft and extending into and journaled in respective hollow axial bearing extensions, an internal thread in said axial opening in said piston to engage the thread on said shaft, and packing interposed between said caps and said hollow axial bearing extensions surounding said tubular piston extensions at the ends of said piston, means at each end of said cylinder to engage said shaft and receive the end thrust thereof as its rotation reciprocates said piston and means to adjust said first means to limit piston, surroundin said shaft and extending into and journaled in respective hollow axial bearing extensions, annular fluid sealing members interposed between said hollow axial bearing extensions and said end caps and surrounding said tubular piston extensions remote from the interior of said cylinder and an internal thread in said axial opening in said piston to engage the thread on said shaft.

4. In a hydraulic actuator, a cylinder, end caps adapted to fit the ends of said cylinder and bolted .thereto, a hollow axial bearing extension on each cap to provide a pair of aligned cylindrical internal bearing surfaces, a threaded shaft passing through said cylinder and into each of said aligned bearings and radially spaced therefrom, a piston with an axial opening in said cylinder, a tubular piston extension on each end of said piston, surrounding said shaft and extending into and journaled in respective hollow axial bearing extensions, annular fluid sealing members interposed between said hollow axial bearing extensions and said end caps and surrounding said tubular piston extensions remote from the in terior of said cylinder and an internal thread in said axial opening in said piston to engage the thread on said shaft, means at each end of said cylinder to engage said shaft and receive end thrust thereof as its rotation reciprocates said piston.

5. In a hydraulic actuator, a cylinder, end caps adapted to fit the ends of said cylinder and bolted thereto, a hollow axial bearing extension on each cap to provide a pair of aligned cylindrical internal bearing surfaces, a threaded shaft passing through said cylinder and into each of said aligned bearings and radially spaced therefrom, a piston with an axial opening in said cylinder, a tubular piston extension on each end of said piston, surrounding said shaft and extending into and journaled in respective hollow axial bearing extensions, annular fluid sealing members interposed between said hollow axial bearing extensions and said end caps and surrounding said tubular piston extensions remote from the interior of said cylinder and an internal thread in said axial opening in said piston to engage the thread on said shaft, means at each end of said cylinder to engage said shaft and receive end thrust thereof as its rotation reciprocates said piston, second means to adjust said first means to limit axial play between said shaft and said cylinder.

GORDON W. HARDY.

REFERENCES CITED The following references are of record in-the file of this patent:

UNITED STATES PATENTS Number Name Date 616,756 Williamson Dec. 27, 1898 1,457,156 Frock May 29, 1923 1,937,485 Davis Nov. 28, 1933 2,014,195 McCollum Sept. 10, 1935 2,204,649 Barnhart June 18, 1940 2,287,960 Ballard June 30, 1942 2,305,302 Mazur Dec. 15, 1942 2,334,383 Carr Nov. 16, 1943 2,344,473 Stevenson Mar. 14, 1944 2,360,539 Ballard Oct. 17, 1944 

